Many built-in functions accept a regex pattern as an argument. Furthermore, any subroutine can accept a string yet treat it as a regex pattern. This could be done, for example, by passing the string to the match operator (m//). Because regex patterns are encoded as regular strings, it is tempting to assume that a string literal will be treated as if a regex that matched only that string literal were supplied. Unexpected function behavior can result if the string contains characters that have special meanings when the string is treated as a regex pattern. Therefore, do not pass strings that are not clearly regex patterns to a function that takes a regex.
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